1. Field of the Invention
The present invention relates to a color value acquiring method, a color value acquiring apparatus, an image processing method, an image processing apparatus, and a recording medium, for making color adjustment of a print based on identification information of a color patch selected as a color that is closest to a designated color, from a color chart having a plurality of color patches containing a reference color.
2. Description of the Related Art
With significant advances in inkjet technology in recent years, it has become possible for inkjet printers to produce large color prints of high quality at high speeds. Inkjet printers are not only popular for private or home use, but nowadays also are widely used in commercial applications. Inkjet printers make it possible to print on POP (point of purchase) posters, wall posters, large-size mediums such as outdoor advertisements and billboards, roll mediums, and thick hard mediums.
There are a wide variety of print mediums (hereinafter also referred to as “mediums”) available for use in prints to meet various commercial demands. For example, such print mediums include paper mediums, such as synthetic paper, thick paper, aluminum-evaporated paper, etc., resin mediums such as those made of vinyl chloride, PET, etc., and tarpaulin paper made of woven fiber cloth with synthetic resin films applied to both surfaces thereof.
Since advertisement prints are expected to be effective to arouse consumers' motivation to buy advertised products through visual sensations of the consumer, the color finish of such prints is of particular importance. Heretofore, there have been disclosed various color matching technologies, such as a method of generating an ICC (International Color Consortium) profile, a method of adjusting a designated color, etc., as a print color managing means. Such color matching technologies are applicable not only to inkjet printers but also to all types of digital printers, including those based on electrophotographic and thermosensitive principles, together with their peripheral devices across the board.
The method of adjusting a designated color referred to above comprises a method of making fine color adjustments of an area of interest in an image in order to bring the color into substantial conformity with a given color (designated color) designated by a color sample of color chips, while maintaining the color balance of the image as a whole. There have been disclosed various methods of adjusting a designated color.
For example, Japanese Laid-Open Patent Publication No. 2000-217007 discloses a method of bringing the impression of a designated color displayed on a display device and the impression of a color printed by a printing machine into conformity with each other. Specifically, Japanese Laid-Open Patent Publication No. 2000-217007 discloses a display window displayed on the display device, in which the displayed color is changeable, and a printed color chart of 27 colors, which are thought to be close to a designated color that is displayed (see FIGS. 4 and 5 of Japanese Laid-Open Patent Publication No. 2000-217007).
Also, in Japanese Laid-Open Patent Publication No. 2000-217007, the operator sets a designated color that is to be displayed in the display window, presses a print button to print the color chart on the printing machine, selects one of the 27 colors of the color chart, which is closest to the designated color, and enters the number of the closest color into the display device, for thereby strictly approximating the impression of the designated color displayed in the display window by the impression of the color printed on the printing machine.
The 14th color at the center of the color chart of 27 colors represents a color of C, M, Y values that corresponds to the designated color, whereas the other colors of the color chart have C, M, Y components that are slightly different from each other by small quantities ΔC, ΔM, ΔY (see FIG. 7 of Japanese Laid-Open Patent Publication No. 2000-217007).
Prints produced by inkjet printers may not endure in severe environments because the images thereof are not highly durable, particularly in terms of abrasion resistance and toughness. For example, such prints are used for sign-display.
Specifically, in exhibition sites that are exposed to high intensity radiant light at all times, color images of displayed prints tend to become gradually discolored because the dyes included in the inks are gradually decomposed by chemical reactions. Also, in display modes where prints are applied to indoor floors, color images of the prints are likely to become damaged because the print surfaces become abraded by people walking on the floors.
Attempts have been made to increase the durability of print images in such applications by covering the image-formed surfaces of prints with protective films such as laminate films, which are functionally treated by the addition of an ultraviolet absorbent, or through an embossing process. The thus-obtained print will be hereinafter referred to as “a protective-film-covered print”.
However, the results of investigation and research conducted by the inventor of the present invention have indicated that, although the laminate film has high transmittance, the spectral transmittance thereof is not necessarily flat within a visible wavelength range, and hence the appearance of printed color images that are covered with the laminate film tends to vary to a non-negligible extent, depending on whether the print is covered with a laminate film or not. It also has been discovered that there are many types of commercially available laminate films, which exhibit different spectral transmittances.
In the method and the apparatus disclosed in Japanese Laid-Open Patent Publication No. 2000-217007, various prints having various laminate films covering image-formed surfaces thereof (i.e., various protective-film-covered prints) have to be visually evaluated, in order to adjust a designated color with respect to a protective-film-covered print. However, if colors are to be strictly adjusted with respect to all combinations of laminate films and prints, then it becomes highly tedious and time-consuming to prepare such samples. Further, repetition of such process results in waste of material cost of the laminate film, disadvantageously.
Also, it is well known that appearance of a print varies depending on the spectral radiance distribution of an observational light source. Similarly, in order to adjust a designated color with respect to a print that is exhibited out of doors, the print has to be visually evaluated under the light source of the exhibition site. In this case, with each printing, the printed color chart has to be carried to the exhibition site, which is highly tedious.